JPH08312539A - Internal gear pump - Google Patents

Abstract

(57) [Summary] [Purpose] Achieves both pulsation suppression and increased discharge rate, and improves volumetric efficiency. Further, it is possible to provide an internal gear pump having a variable discharge amount. [Configuration] The total number of outer teeth 42 of the inner rotor 40 and the total number of inner teeth 52 of the outer rotor 50 are made equal. External teeth 4
2 has a shape in which the tooth tips project toward the forward side in the rotation direction of the inner rotor 40, and the inner tooth 52 has a shape in which the tooth tips project toward the backward side in the rotation direction of the outer rotor 50. Further, the outer rotor 5 with respect to the outer peripheral surface of the inner rotor 40 in a state where the rotation centers of the two rotors 40, 50 coincide with each other.
The peripheral surface shapes of both rotors are set so that the distance in the normal direction of the inner peripheral surface of 0 is constant over the entire circumference.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal gear pump provided in a vehicle transmission or the like.

[0002]

2. Description of the Related Art FIG. 17 shows an example of a conventional internal gear pump (trochoid pump in the illustrated example).

The illustrated internal gear pump includes a pump housing 90 and a pump cover (not shown), and an inner rotor 91 and an outer rotor 92 meshing with each other are housed in a rotor working chamber formed in the pump housing 90. Outer rotor 92 is rotatably held in the pump housing 90 side, the inner rotor 91 is fixed around the unillustrated pump drive shaft, and the rotation center axis O ₂ of the rotation axis O ₁ and the outer rotor 92 of the inner rotor 91 Is deviated by a predetermined eccentric amount e. A suction groove 93 and a discharge groove 94 are formed on the inner side surface of the pump housing 90. The suction groove 93 communicates with an unillustrated pump suction port via a suction passage 95, and the discharge groove 94 has a discharge passage 96. It is communicated with a pump discharge port (not shown) through.

On the outer peripheral surface of the inner rotor 91, a plurality of trochoidal outer teeth 91a are arranged side by side in the circumferential direction, while on the inner peripheral surface of the outer rotor 92, one trochoidal outer tooth 91a is provided. Many trochoidal internal teeth 92a are formed. The eccentricity e is set so that at least a part of the trochoid outer teeth 91a almost always contacts somewhere on the inner peripheral surface of the outer rotor 92 (actually, they are separated with a minute gap therebetween).

In this internal gear pump, when the inner rotor 91 is driven to rotate about the rotation center axis O ₁ , the outer rotor 92 meshing with the inner rotor 91 rotates about the rotation center axis O _{2 in the} same direction, and both rotors 91 are rotated. , 92 are formed with a plurality of compression chambers C1, C2 ,.
In the state shown in the figure, after the oil is sucked into the compression chamber C1 through the suction groove 93, the volume of the compression chamber C1 is successively reduced to the same volume as that of the illustrated compression chambers C2, C3, C4 as the rotor rotates. As a result, the oil trapped in the compression chamber C1 is discharged from the discharge port (not shown) through the discharge groove 94 through the discharge passage 96 while being pressurized.

[0006]

The above internal gear pump has the following problems to be solved.

A) In the internal gear pump, in order to reduce the pulsation, the number of teeth may be set as large as possible.
However, in the internal gear pump having a general tooth profile such as the trochoidal tooth profile shown in the figure, the tooth height must be reduced as the number of teeth is increased, and the discharge amount is reduced accordingly. . Therefore, it is virtually impossible to achieve both the suppression of pulsation and the increase in discharge amount.

B) In the above internal gear pump, both rotors 9
Since rotation failure occurs when 1 and 92 mesh with each other over the entire circumference, in order to prevent such meshing over the entire circumference, a small gap is secured between the outer peripheral surface of the inner rotor 91 and the inner peripheral surface of the outer rotor 92. There is. Therefore, the compression chambers C1, C2, ... Are not strictly closed, and oil easily leaks from both end points H1, H2, H3, H4 ,. is there. On the other hand, on the suction side, there is a demand to separate the tooth surfaces of both rotors 91, 92 as much as possible in order to improve the suction efficiency. In the conventional internal gear pump, however, both rotors 91, 92 should be separated greatly. It is difficult.

C) In order to change the discharge amount of the internal gear pump, the eccentric amount e of the rotation center axes O ₁ and O ₂ may be changed. 92
Relative displacement in the radial direction is almost impossible, and it is extremely difficult to make the discharge amount variable.

Conventionally, a variable displacement type vane pump has been already provided, but the internal gear pump has fewer parts than the vane pump, has a simple structure, is easy to assemble, and is small and lightweight. This internal gear pump is required to be of a variable displacement type because it has the advantage of being able to do so.

An object of the present invention is to provide an internal gear pump capable of solving the above problems.

[0012]

SUMMARY OF THE INVENTION According to the present invention, a housing having suction and discharge grooves on its inner side surface is rotatably accommodated in the housing, and a plurality of inner teeth are arranged side by side in the circumferential direction on the inner peripheral surface. The outer rotor, and outer teeth that mesh with the outer rotor from the inner side are arranged in parallel on the outer peripheral surface, and the inner rotor is rotatably housed inside the outer rotor around a point different from the center of rotation of the outer rotor. The two rotors rotate in synchronization with each other and the outer teeth mesh with each other, so that compression chambers are sequentially formed between the inner teeth and the outer teeth, and fluid is sucked into the compression chambers through the suction grooves and from the compression chambers. In an internal gear pump configured such that fluid is discharged to the discharge groove, the total number of external teeth and the total number of internal teeth are made equal, and the outer teeth of the inner rotor are shaped such that their tips have outer teeth. Of the outer rotor, the inner teeth of the outer rotor are shaped so that the tooth tips thereof project to the backward side of the outer rotor in the rotation direction, and the rotation centers of both rotors are matched. In this state, the shapes of the outer peripheral surface of the inner rotor and the inner peripheral surface of the outer rotor are set so that the distance in the normal direction of the inner peripheral surface of the outer rotor to the outer peripheral surface of the inner rotor is constant over the entire circumference (claim 1). .

It is preferable that the tips of the external teeth are arcuate (claim 2).

In this case, the length of the arc portion is set so that the angle formed by the tangent line at the end point to the straight line connecting the inner end of the arc portion in the radial direction of the rotor and the center of rotation of the inner rotor is approximately 90 °. Alternatively, the radius of curvature of the tooth tip arc may be set to 1/1 / the linear distance between the end point on the inner side in the rotor radial direction and the end point on the outer side in the rotor radial direction of this arc portion.
It is further preferable to set it to be larger than 2 (claim 4).

Further, the tips of the internal teeth are also preferably arcuate (claim 5).

Also in this case, the length of the arc portion is set so that the angle formed by the tangent line at the end point to the straight line connecting the outer end of the arc portion in the radial direction of the rotor and the rotation center of the outer rotor is approximately 90 °. (Claim 6),
The radius of curvature of the tooth tip arc is defined as 1 of the linear distance between the end point on the inner side in the rotor radial direction and the end point on the outer side in the rotor radial direction of this arc portion.
It is further preferable to set it larger than / 2 (claim 7).

In the internal gear pump, the outer rotor extends radially outward from the peripheral surface of its inner teeth, is formed between the inner teeth and the outer teeth, and its volume increases as the two rotors rotate. It is more preferable to form a rotor suction passage that communicates the expansion chamber with the suction groove.

As the rotor suction passage, a rotor suction groove is preferably formed on a side surface of the outer rotor (claim 9).

Further, in the housing, a communication passage communicating with the suction groove is formed on an inner circumferential surface of the housing located radially outside of the outer rotor, and the rotor suction passage is extended to the outer circumferential surface of the outer rotor to form the communication passage. By forming the shape that communicates with the expansion chamber, a more excellent effect as described below can be obtained (claim 10).

In the inner rotor, an expansion chamber that extends inward in the rotor radial direction from the outer peripheral surface of the outer teeth and is formed between the outer teeth and the inner teeth to increase in volume with the rotation of both rotors, and A rotor suction passage communicating with the suction groove may be formed (claim 11).

Also in this case, the rotor suction passage is
A rotor suction groove is preferably formed on the side surface of the inner rotor (claim 12).

Further, in the housing, the suction groove is circumferentially extended in a region radially inward of the outer teeth of the inner rotor, and the rotor suction groove is formed so as to communicate the extended portion with the expansion chamber. By doing so, a more excellent effect as described below can be obtained (claim 13).

In the internal gear pump, it is possible to configure the housing so that the eccentricity between the center of rotation of the inner rotor and the center of rotation of the outer rotor is variable (claim 14).

Specifically, the housing is composed of a housing body and a cam ring provided inside the housing body so as to be swingable about a point deviated from the center of rotation of the rotors. While the outer rotor is rotatably held, the inner rotor is connected to a pump drive shaft, and the rotation drive center of the inner rotor and the rotation center of the outer rotor are relatively displaced as the cam ring swings. Those are preferable (claim 15).

[0025]

In the internal gear pump according to the first aspect of the present invention, both rotors rotate synchronously in a state in which the outer teeth of the inner rotor whose tooth tips project forward in the rotational direction and the inner teeth of the outer rotor projecting backward in the rotational direction mesh with each other. With the same number of inner teeth and outer teeth and the rotation centers of both rotors are aligned, the distance between the inner and outer teeth of both rotors in the normal direction is constant. Therefore, unlike a conventional tooth profile such as a trochoidal tooth profile, it is possible to increase only the number of teeth without reducing the tooth height. Therefore, the ejection amount can be increased while increasing the number of teeth. In addition, in the suction area, a larger gap can be secured between the inner teeth and the outer teeth than the conventional internal gear pump,
While the suction efficiency can be increased accordingly, the outer teeth and the inner teeth can be brought into close contact with each other in the discharge area, and the volume efficiency can be improved accordingly.

More specifically, in the internal gear pump according to the second aspect, the arcuate surface of the tip of the external tooth comes into contact with the internal tooth and smoothly slides to form a compression chamber between the two teeth. , As well as
In the internal gear pump according to the fifth aspect, the compression chamber is formed between the teeth while the arcuate surfaces of the tooth tips of the internal teeth come into contact with the external teeth and slide smoothly.

Here, the angle formed by the tangent line at the end point with respect to the straight line connecting the end point on the inner side in the radial direction of the rotor of the arcuate portion of the outer tooth tip and the rotation center of the inner rotor is the direction of rotation of the outer tooth tip. It can be set freely within the range of projecting to the advancing side, but the larger this angle (that is, the larger the arc area is secured), the greater the degree to which the tooth tips project to the advancing direction in the rotational direction, The maximum compression chamber volume increases by that amount, and the discharge amount also increases. Therefore, by setting the angle to about 90 ° as in the third aspect, it is possible to obtain a substantially maximum discharge amount.

The radius of curvature of the tip arc of the external tooth is
Although it may be set to 1/2 of the linear distance between the end point on the inner side in the radial direction of the arc and the end point on the outer side in the radial direction of the rotor,
As set forth in claim 4, by setting the distance larger than ½ of the linear distance, the gap in the vicinity of the contact point between the circular arc portion and the internal tooth becomes small, and the leakage of fluid from the compression chamber is correspondingly reduced. It is less likely to occur.

Similarly, the angle formed by the tangent line at the end point with respect to the straight line connecting the inner end point of the arc portion of the tooth tip of the inner tooth in the radial direction of the rotor and the center of rotation of the outer rotor is the inner tooth tooth. It can be set freely within the range where the tip projects backward in the rotational direction. However, the larger this angle (that is, the larger the arc area is secured), the degree to which the tooth tip projects forward in the rotational direction. Becomes larger, the maximum compression chamber volume increases correspondingly, and the discharge amount also increases,
By setting the angle to about 90 ° as in the sixth aspect, it is possible to obtain a substantially maximum discharge amount.

The radius of curvature of the tip arc of the internal tooth is also
Although it may be set to 1/2 of the linear distance between the end point on the inner side in the radial direction of the arc and the end point on the outer side in the radial direction of the rotor,
As set forth in claim 7, by setting the distance larger than ½ of the linear distance, the gap in the vicinity of the contact point between the arc portion and the internal tooth becomes small, and the leakage of the fluid from the compression chamber is correspondingly reduced. It is less likely to occur.

In the internal gear pump, a compression chamber is formed between the external tooth and the internal tooth, and at the same time, a volume is generated between the external tooth and the internal tooth adjacent to the compression chamber as the rotor rotates. To form an expansion chamber. If the expansion chamber is sealed, the pressure inside the expansion chamber will decrease sharply as the volume of the expansion chamber expands, which may cause rotor rotation resistance and waste power.
However, in the internal gear pump according to claim 8, a rotor suction passage is formed in the outer rotor so as to extend from the inner teeth of the outer rotor to the outer side in the radial direction of the rotor. Since the fluid is sucked through the suction passage, the pressure in the expansion chamber is sufficiently maintained. Moreover, since the working fluid flows into the compression chamber through the rotor suction passage until just before the compression chamber starts to be compressed, the suction efficiency is increased. In addition, the weight of the outer rotor is reduced by the amount of the rotor suction passage formed, and the rotational power is reduced accordingly.

Here, in the internal gear pump according to the ninth aspect, since the rotor suction groove is formed on the side surface of the outer rotor as the rotor suction path, the rotor suction groove is formed on the side surface of the outer rotor. Shear resistance is reduced,
Rotational power is saved.

Further, in the internal gear pump according to a tenth aspect of the present invention, a communication passage communicating with the suction groove is formed on an inner peripheral surface of the housing located radially outside of the outer rotor, and the communication passage and the expansion chamber are formed. Since the rotor suction passage reaches the outer peripheral surface of the outer rotor so as to communicate with the outer suction passage, suction can be performed by the rotor suction passage over a wider rotation region, and the suction efficiency is further increased.

In the internal gear pump according to the eleventh aspect, since the expansion chamber and the suction groove are communicated with each other by the rotor suction passage formed in the inner rotor, the same as the eighth aspect.
While the pressure in the expansion chamber is maintained sufficiently, the working fluid flows into the compression chamber through the rotor suction passage until just before the compression chamber starts to be compressed, so that the suction efficiency is improved. In addition, the weight of the outer rotor is reduced by the amount of the rotor suction passage formed, and the rotational power is reduced accordingly.

Further, in the internal gear pump according to the twelfth aspect, since the rotor suction groove is formed on the side surface of the inner rotor as the rotor suction path, the rotor suction groove is formed.
Similar to the described internal gear pump, the shear resistance of the working fluid on the side surface of the outer rotor is reduced by the formation of the rotor suction groove, and the rotational power is reduced.

Further, in the internal gear pump according to the thirteenth aspect, the suction groove is extended in the housing in the circumferential direction, and the rotor suction groove is formed so as to communicate the extension portion with the expansion chamber. Therefore, it is possible to perform suction through the rotor suction passage over a wider rotation region, and the suction efficiency is further increased. Moreover, since the extension portion is formed in the region radially inward of the outer teeth of the inner rotor, it does not adversely affect the ejection through the ejection groove.

As described above, in the internal gear pump of the present invention, a constant clearance is formed between the two rotors in the state where the center of rotation of the inner rotor and the center of rotation of the outer rotor are matched. Since the tooth shapes of both rotors are set, it is possible to relatively displace the rotation centers of both rotors by the gap. Therefore, claim 14
As described above, by configuring the housing such that the eccentric amount between the rotation center of the inner rotor and the rotation center of the outer rotor is variable, the pump discharge amount can be adjusted.

More specifically, in the internal gear pump according to the fifteenth aspect, the cam ring is rocked with respect to the housing body in a state where the inner rotor is connected to the pump drive shaft, so that the cam ring is held by the cam ring. The rotation center of the outer rotor that is present can be displaced relative to the rotation center of the inner rotor (that is, the amount of eccentricity can be changed).

[0039]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. Although an oil pump will be described in this embodiment, the internal gear pump of the present invention can be used for compressing various working fluids other than oil.

The internal gear pump shown here includes a housing body 20. The housing body 20 is composed of a pump housing 21 and a pump cover 22,
Both are joined to each other by a bolt or the like (not shown). A through hole 22a is provided at the center of the pump cover 22 so as to penetrate the pump cover 22 in the axial direction (the left and right direction in FIG. 3).
The drive shaft 23 is inserted into the inside 2a from the outside (left side in FIG. 3) of the pump cover 22. The end of the drive shaft 23 is housed in the housing chamber 26 of the pump housing 21, and its cross section is a modified cross section (a cross section surrounded by a combination of straight lines and arcs in the illustrated example).

As shown in FIG. 4, the pump housing 21
In the side surface (inner side surface) facing the storage chamber 26,
A suction groove 28 and a discharge groove 29 are formed, and these are connected to the pump suction port and the pump discharge port, respectively, via oil passages (not shown).

A cam ring 30 as shown in FIG. 5 is provided in the accommodation chamber 26. This cam ring 3
While a substantially semicircular fitting protrusion 34 is formed at a specific position on the outer peripheral surface of 0, a substantially semicircular fitting recess 24 is also formed at a specific position on the inner peripheral surface of the accommodation chamber 26. With the fitting protrusion 34 fitted in the fitting recess 24, the entire cam ring 30 can swing about the swing center axis Oc in the approximate center of the fitting protrusion 34. It is accommodated in the accommodation chamber 26.

As shown in FIG. 4, stoppers 38 and 39 are provided at two locations on the inner peripheral surface of the accommodating chamber 26, and when the cam ring 30 is in contact with the stopper 39 as shown in FIG. The cam ring 30 is held at the lowermost position,
As shown in FIG. 5, the cam ring 30 is held at the uppermost position in a state where the cam ring 30 is in contact with the stopper 38. Further, spring seats 32 and 27 are formed at positions facing each other on the outer peripheral surface of the cam ring 30 and the inner peripheral surface of the accommodation chamber 26, and a spring 37 is provided between the spring seats 32 and 27. , The cam ring 3 by the elastic force of this spring 37
0 is urged downward.

The outer rotor 50 is rotatably held inside the cam ring 30, and the inner rotor 40 is fixed to the end of the pump drive shaft 23 inside the outer rotor 50.

As shown in FIG. 6, the inner rotor 40 has a through hole 4 having a shape capable of being fitted with the pump drive shaft 23.
4, the through hole 44 and the pump drive shaft 23 are fitted to each other, and the entire inner rotor 40 is fixed to the pump drive shaft 23 so as not to rotate relative to each other. On the outer peripheral surface of the inner rotor 40, a plurality of outer teeth 42 are arranged side by side in the circumferential direction, and each outer tooth 42 has a shape in which the tip of each tooth protrudes toward the forward side in the inner rotor rotation direction (clockwise direction in FIG. 6). It is said that.

On the other hand, the outer rotor 50 has a ring shape as shown in FIG. 7, and the same number of inner teeth 52 as the outer teeth 42 are arranged side by side in the circumferential direction on the inner peripheral surface thereof. . Each inner tooth 52 has a shape in which the tip of the tooth protrudes toward the backward side in the outer rotor rotation direction (clockwise direction in FIG. 7).

Details of the shapes of the outer teeth 42 and the inner teeth 52 are shown in FIG. The outer peripheral surface of the outer tooth 42 has an arc surface 42a having a radius of curvature equal to ½ of the maximum outer diameter of the inner rotor 40.
And a convex arc surface 42b connecting the end point P1 of the arc surface 42a and a point P2 further away from the end point P1 in the radial direction of the rotor, and the end point P2 of the arc surface 42b and the minimum outer diameter of the inner rotor 40. It is composed of a concave arc surface 42c connecting to the point P3 located, and the arc surface 42b is a tooth crest surface.

On the other hand, as shown in FIG. 9, the inner peripheral surface of the outer rotor 50 has the inner rotor 4 with the rotation centers O ₁ and O _{2 of the} rotors 40 and 50 aligned with each other.
The distance in the normal direction to the outer peripheral surface of 0 is set to be a constant distance δ over the entire circumference. Therefore, the inner peripheral surface shape of the inner teeth 52 of the outer rotor 50 is, as shown in FIG. 8, a concave arc surface 52b facing the arc surface 42b of the outer teeth 42 and the arc surface 42c of the outer teeth 42. And a circular arc surface 52d facing the outer peripheral surface of the minimum outer diameter of the inner rotor 40. The circular arc surface 52c constitutes a tooth tip surface, and the circular arc surface 52d is the minimum of the outer rotor 50. It has a radius of curvature equal to the inner diameter.

In this embodiment, the radius of curvature of the arcuate surface 42b is set equal to 1/2 of the linear distance between the end points P1 and P2, and the central angle is set to 180 °. That is, the arc surface 42b is a semicircular surface. Similarly,
The radius of curvature of the arc surface 52c is also set equal to 1/2 of the linear distance between the end points Q2 and Q3, and is a semicircular surface having a central angle of 180 °. That is, in this embodiment, the rotation center axes O ₁ and O ₂ of the rotors 40 and 50 are aligned with each other, and the rotation center axes O ₁ and O ₂ and the arc surfaces 42b and 42c are formed.
End points P1, P2, P3, and circular arc surfaces 52b, 52c
The shapes of the outer teeth 42 and the inner teeth 52 are set so that the respective end points Q1, Q2, Q3 of all are substantially aligned on the same straight line L, and the tangent line L _{4 at} the rotor radial inner end point P2 of the arc surface 42b is set.
The angle theta ₄ between the straight line L, and the angle theta ₅ between the tangent line L ₅ and the straight line L in the rotor radially outside end point Q2 arcuate surfaces 52c, are both approximately 90 °.

As described above, since the outer rotor 50 is held inside the cam ring 30, the swinging of the cam ring 30 changes the eccentricity e of both rotors 40 and 50 and the discharge amount. However, in this embodiment, as shown in FIGS. 1 and 2, an eccentricity adjusting device 60 is automatically provided for automatically adjusting the eccentricity e in order to keep the discharge amount constant.

The eccentricity adjusting device 60 includes a sleeve 61.
And a spool 62 accommodated in the sleeve 61. The sleeve 61 has a discharge oil introduction passage 63A, a discharge oil discharge passage 63B, an eccentricity adjustment oil passage 64A, and a drain discharge passage 64B as oil passages that communicate the inside and the outside thereof, and the discharge oil introduction passage 63A is a pump. The eccentricity adjustment oil passage 64A is connected to the discharge passage, and is connected to the back pressure chamber 26a formed in the accommodation chamber 26 at a position opposite to the side where the spring 27 is provided. The spool 62 has a discharge oil passage 62a extending in the axial direction at the center thereof, a throttle oil passage 62b is formed on the downstream side of the discharge oil passage 62a, and the spool 62 has an entire circumference on the outer peripheral surface thereof. Circumferential groove 6
2c is formed. A spring 66 is accommodated in the spool accommodating chamber, and the elastic force of the spring 66 urges the entire spool 62 to the left side (the discharge oil introducing passage 63A side) in FIGS. 1 and 2.

Next, the operation of this internal gear pump will be described. First, when the pump is not operating, the cam ring 30 is held at the lowermost position in FIG. 1 by the elastic force of the spring 37, and the eccentricity e of the rotation center axes O ₁ and O ₂ of both rotors 40 and 50 is To be the maximum. In this state, the pump drive shaft 23
Is driven to rotate clockwise in FIGS. 1 and 2, the inner rotor 40 fixed thereto is also driven to rotate in the same direction. Further, while the outer teeth 42 of the inner rotor 40 and the inner teeth 52 of the outer rotor 50 mesh with each other, the outer rotor 50 also rotates in the same direction.

At this time, as shown in FIG. 10, in the suction region (the region where the suction groove 28 is formed; the right region in FIG. 10), the tips of the outer teeth 42 are largely separated from the inner peripheral surface of the outer rotor 50. are doing. Therefore, the hydraulic oil easily enters from the suction groove 28 between the teeth 42 and 52, and the suction efficiency is improved accordingly.

On the other hand, when the discharge area (area where the discharge groove 29 is formed; left side area in FIG. 10) is entered,
The tips of the outer teeth 42 start to come into contact with the inner teeth 52 at positions outside the tips of the rotor in the radial direction of the rotor.
The compression chambers C1, C2, C3, C4 ... Are formed between each other. Here, the compression chamber C1 formed at the start of contact between the teeth 42 and 52 has the maximum volume, and thereafter, the volume of the compression chamber C1 is equal to that of the illustrated compression chambers C2, C3, and C4. By reducing the volume, the hydraulic oil in the compression chamber is discharged from the discharge groove 29 while being pressurized.

Here, while the rotor rotation speed is low and the discharge amount is small, in the eccentricity adjusting device 60, the discharge oil introducing passage 63 is provided.
Since the flow rate of the hydraulic oil introduced from A to the discharge oil passage 62a of the spool 62 is small, the flow resistance in the throttle oil passage 62B is also low, so that the spool 62 is held in the position of FIG. 1 by the elastic force of the spring 66. . In this state, the circumferential groove 62c of the spool 62 is completely opposed to the eccentricity adjusting oil passage 64A and the eccentricity adjusting oil passage 64A is blocked, and the cam ring 30 is moved to the bottom end of FIG. It is held at the position (that is, the position where the eccentricity e and the ejection amount are the largest).

After that, when the rotation speed of the rotor increases and the pump discharge amount increases, the flow rate of the working oil introduced from the discharge oil introducing passage 63A to the discharge oil passage 62a of the spool 62 in the eccentricity adjusting device 60 also increases. Throttle oil passage 62B
The flow resistance at
It is displaced to the position shown in FIG. 2 (that is, to the right) against the elastic force of. In this state, the eccentricity adjusting oil passage 64A communicates with the discharge oil introducing passage 63A, so that part of the discharge oil is introduced into the back pressure chamber 26a through the eccentricity adjusting oil passage 64A.
As a result, the pressure in the back pressure chamber 26a increases, and the cam ring 30 is displaced upward against the elastic force of the spring 37. Therefore, the rotation center axes O ₁ and O _{2 of} both rotors 40 and 50 are
The eccentric amount e of is reduced and the discharge amount is reduced.

According to this internal gear pump, the following excellent effects can be obtained as compared with the conventional internal gear pump.

(A) In the conventional internal gear pump, the discharge amount tends to decrease as the number of teeth increases, and therefore pulsation suppression and discharge amount increase cannot both be achieved. Since the internal gear pump can increase only the number of teeth without reducing the tooth height, the number of teeth can be increased and the discharge amount can be increased while avoiding pulsation. Actually, with the tooth profile setting similar to the above, as shown in FIGS. 11 (a), (b), (c) and (d), the internal gear pump having the number of teeth Z of 8, 9, 10, 11 is 1 from the compression chamber area. As a result of calculating the discharge amount per rotation, when Z = 8, the discharge amount is 15.0cc / rev, Z
= 9, the discharge rate is 15.8cc / rev, Z = 10, the discharge rate is 1
At 6.7 cc / rev and Z = 11, the discharge rate was 17.5 cc / rev, and it was confirmed that the discharge rate increased as the number of teeth Z was increased.

(B) In the conventional internal gear pump, it was not possible to extremely widen the gap between the teeth in the suction region, and conversely, to make the teeth closely contact in the discharge region. In the internal gear pump, as shown in FIG. 10, a large gap can be secured between the outer teeth 42 and the inner teeth 52 in the suction region, and the suction efficiency can be improved by that amount, while the outer teeth 42 and the inner teeth 52 can be increased in the discharge region. It is possible to prevent the hydraulic oil from leaking from the compression chamber by bringing the internal teeth 52 into close contact with each other, and the volumetric efficiency can be improved accordingly.

(C) In the conventional internal gear pump, since the teeth are in close contact with each other over the entire circumference, it is almost impossible to change the eccentricity of both rotors. In the internal gear pump, since the eccentricity e can be changed by the gap δ shown in FIGS. 8 and 9, it is possible to configure the internal gear pump as a variable displacement type pump. However, it goes without saying that the internal gear pump of the present invention can also be used as a constant capacity pump.

(D) Since the tooth tips of the outer teeth 42 and the inner teeth 52 are arcuate surfaces, these tooth tips can smoothly slide on the peripheral surface of the other party, and the rotation resistance is reduced accordingly.

In the internal gear pump of this embodiment,
As shown in FIG. 10, the tooth tips of the outer teeth 42 come into contact with the peripheral surfaces of the inner teeth 52 to form the compression chambers C1, C2, ... Tooth tip is external tooth 4
The expansion chambers E1, E2, E3, E4, ... If the expansion chamber is sealed, the pressure inside the expansion chamber will decrease sharply as the volume of the expansion chamber expands, which may cause rotor rotation resistance and waste power.

However, the above-mentioned FIGS. 1, 2, 3, 5, 7, 10
As shown in FIG. 5, the outer rotor 50 is formed with a rotor suction groove 51 extending from its inner teeth 52 to the outer peripheral surface of the outer rotor 50, while the communication groove 36 is formed in the inner peripheral surface of the cam ring 30. Groove 36 and the expansion chamber E
1, E2, ... Are communicated with the rotor suction grooves 51 through the rotor suction grooves 51 along with the expansion of the expansion chambers E1, E2. Can be inhaled. For this reason, not only can the pressure in the expansion chamber be maintained sufficiently, but hydraulic oil can flow into the compression chambers C1, C2 ... Through the rotor suction groove 51 until just before compression starts. Minute inhalation efficiency can also be improved. In addition, the weight of the outer rotor 50 can be reduced by the amount of the formation of the rotor suction groove 51,
Further, the shear resistance of the hydraulic oil on the side surface of the rotor is reduced, and the rotary power can be reduced accordingly. Further, as shown in FIGS. 3 and 4, an auxiliary groove 25 that directly connects the suction groove 28 and the communication groove 36 to the pump housing 21 and the pump cover 22.
By forming A and 25B respectively, the inhalation effect becomes more remarkable.

Here, it is preferable to ensure the hermetic sealing of each compression chamber even if the rotor suction groove 51 is formed. For that purpose, the outlet position of the rotor suction groove 51 is set as shown in FIG. Good. That is, the rotor radial inner edge X1 and the radial outer edge X2 of the rotor suction groove 51 outlet are provided.
The position of may be set as follows.

A) At the internal tooth 52 that has started to contact the external tooth 42, both outlet edges X1 and X2 of the rotor suction groove 51 are displaced outward in the radial direction of the rotor, or the edge X1 is radially inward from the contact point T1. It is made to coincide with the contact point T1.

B) Letting T2 be the contact point on the outer side in the rotor radial direction after the inner tooth and the outer tooth 42 that precedes the outer tooth 42 and the inner tooth 52 that have started contact by one tooth in the rotor rotation direction, the rotor suction groove 51. Both exit edges X1 and X2 of the contact point T
2 radial inner or radial outer edge X2
Should match T2.

The rotor suction passage formed in the outer rotor 50 is not limited to the rotor suction groove 51, and for example, a rotor suction hole extending from the inner teeth 52 to the outer peripheral surface of the outer rotor 50 is formed at the center of the outer rotor 50 in the thickness direction. You may pierce. However, as shown, the outer rotor 50
If the rotor suction groove 51 is formed on the side surface of the outer rotor, not only the manufacturing becomes easier, but also the shear resistance on the outer rotor side surface is reduced by the amount of the formation of the rotor suction groove 51, and the rotational power can be further reduced.

Further, in this embodiment, in FIG. 8, the angle θ ₄ formed by the tangent line L _{4 at} the inner end point P2 of the arc surface 42b and the straight line L in the rotor radial direction, and the arc surface 5
The angle θ ₅ formed by the tangent line L _{5 at} the outer end point Q2 of 2c and the straight line L in the rotor radial direction is set to about 90 °, respectively, but these angles are in a range larger than 0 ° (that is, the tip of the tooth rotates). It can be set freely within the range that projects in the direction). In FIG. 8, the tooth profile shown by the chain double-dashed line has a θ ₄ of 90
The angle between the tangent line L ₄ ′ at the inner end point P ₂ ′ of the arc surface 42 b and the end point P ₂ ′ and the straight line L ′ passing through the rotor center is set to θ ₄ ′. ing. However, the closer the angles θ ₄ and θ ₅ are brought to 90 °, the greater the degree to which the tooth tips project in the rotor rotation direction, and the larger the discharge amount accordingly. In fact, FIG.
As shown in (a), (b), (c) and (d), the angle θ ₄ ,
Maximum compression chamber Cmax (mesh in the figure) for internal gear pumps with θ _{5 set} to 90 °, 60 °, 30 °, 0 °
When the volume of was calculated, it was confirmed that the volume was the largest when θ ₄ = θ ₅ = 90 °.

Next, a second embodiment will be described. The internal gear pump of this embodiment differs from the internal gear pump of the first embodiment in the following points.

A) In the first embodiment, the radius of curvature of the arcuate surfaces 42b, 52c forming the tooth crests is set equal to 1/2 of the linear distance between the end points (that is, a semicircle). ), In this embodiment, as shown in FIG.
Instead of the circular arc surfaces 42b and 52c, the radius of curvature R is sufficiently larger than 1/2 of the linear distance between the end points.
′ And 52c ′ are set as the tooth crests, and the arc surface 4
Both ends of 2b 'and 52c' are constituted by arcs having a very small radius of curvature r. In addition, the arc surface 42b
Corresponding to ′ and 52c ′, the radius of curvature of the concave arcuate surfaces 52b ′ and 42c ′ facing them is also set to be larger than ½ of the linear distance between the end points.

According to such a configuration, the arc surfaces 42b,
As compared with the first embodiment in which the radius of curvature of 52c is small, the arc surface 4
Since the gap in the vicinity of the contact point between 2b 'and 52c' and the tooth surface of the opposite side becomes small, the leakage of hydraulic oil from the compression chamber is suppressed by that amount, and the volumetric efficiency is further improved.

B) In the first embodiment, as shown in FIG. 14, the rotor suction groove 51 is formed on the outer rotor 50 side, but in the second embodiment, the outer teeth are formed on the side surface of the inner rotor 40. A rotor suction groove 41 extending from the vicinity of the tooth top of 42 to the inner side in the radial direction of the rotor is formed. further,
The suction groove 28 is extended in the circumferential direction in the region radially inward of the outer teeth 42, and the extension portion 28a and each expansion chamber E1,
The shape of the rotor suction groove 41 is set so as to communicate with E2 and E3, and the discharge groove 29 is formed in a region outside the outer teeth 42 in the rotor radial direction.

With this structure as well, similar to the first embodiment, by sucking the working oil from the extension portion 28a into the expansion chambers E1, ... Through the rotor suction groove 41, the pressure in the expansion chamber can be maintained sufficiently. Without compression chambers C1 and C2
Until the compression starts, the working oil flows into the compression chambers C1 and C2 through the rotor suction groove 41 to improve the suction efficiency, and the weight of the inner rotor 40 is reduced by the formation of the rotor suction groove 41. The shearing resistance of the hydraulic oil on the side surface of the rotor is reduced, and the rotary power can be reduced accordingly.

In particular, in this embodiment, since the suction groove 28 is extended in the circumferential direction, the region which can be sucked into the expansion chambers E1, ... Through the rotor suction groove 41 can be expanded, and a more remarkable effect can be obtained. Has become. Moreover, the extension 28
Since a is formed in the region radially inward of the outer teeth 42, the extension 28a does not adversely affect the discharge of hydraulic oil into the discharge groove 29.

Also in this embodiment, it is preferable to secure the airtightness of each compression chamber while forming the rotor suction groove 41,
For that purpose, it is preferable to set the outlet position of the rotor suction groove 41 as shown in FIG. That is, the positions of the rotor radial inner edge Y1 and the radial outer edge Y2 at the outlet of the rotor suction groove 41 may be set as follows.

A) External tooth 42 which has started to contact internal tooth 52
At (the outer teeth 42 at the moment when the rotor suction groove 41 disconnects from the suction groove 28), the rotor suction groove 4 is located at a position closer to the contact point T1.
Both of the outlet edges Y1 and Y2 of No. 1 are displaced inward in the radial direction of the rotor, or the outer edge Y2 in the radial direction is at the contact point T.
Match with 1.

B) In the next outer tooth 42 (the outer tooth 42 whose rotor suction groove 41 does not face either the suction groove 28 or the discharge groove 29), the contact point T2 between this outer tooth 42 and the inner tooth 52 is The radially inner edge Y1 and the radially outer edge Y2 are sandwiched.

C) Furthermore, the next outer tooth 42 (the compression chamber C2 to be formed already faces the discharge groove 29, and the rotor suction groove 41
Of the outer teeth 42) at the moment when the outer teeth 42 communicate with the suction groove 28, both edges Y are larger than the contact point T3 between the outer teeth 42 and the inner teeth 52.
1 and Y2 are displaced to the outer side in the radial direction of the rotor, or the inner edge Y1 in the radial direction coincides with the contact point T3.

In this embodiment also, the inner rotor 40
As the rotor suction passage formed in the
However, the outer teeth 4 are not provided inside the inner rotor 40, for example.
A rotor suction hole extending from 2 to the side surface of the inner rotor 40 may be formed. However, if the rotor suction groove 41 is formed on the side surface of the inner rotor 40 as shown in the drawing, not only the manufacturing is facilitated, but also the shear resistance of the working oil on the side surface of the outer rotor is reduced by the formation of the rotor suction groove 41, and There is an advantage that power can be further saved.

[0080]

As described above, according to the present invention, the following effects can be obtained.

In the internal gear pump according to the first aspect of the invention, both rotors rotate synchronously in a state in which the outer teeth of the inner rotor whose tooth tips project forward in the rotational direction and the internal teeth of the outer rotor projecting backward in the rotational direction mesh with each other. The number of inner teeth is equal to the number of outer teeth, and the distance between the peripheral surfaces of both rotors in the normal direction is constant with the rotation centers of both rotors aligned. Therefore, there is an effect that the ejection amount can be increased while suppressing the pulsation by increasing the number of teeth. Also,
Unlike conventional gear pumps, in the suction area, a large gap is secured between the inner and outer teeth to improve suction efficiency,
In the ejection area, the outer teeth and the inner teeth can be brought into close contact with each other to improve the volumetric efficiency.

More specifically, in the internal gear pump according to the second and fifth aspects, since the external tooth tip and the internal tooth tip are formed of arcuate surfaces, the circumferences of these tooth tips and the mating tooth are set. It has the effect of smoothing sliding on the surface, reducing rotational resistance, and saving power.

Here, in the internal gear pump according to the third and sixth aspects, the angle formed by the tangent line at the end point with respect to the straight line connecting the end point of the circular arc portion on the inner side in the rotor radial direction and the rotation center of the inner rotor, Since the angle formed by the tangent line at the end point to the straight line connecting the end point of the arc portion on the outer side in the radial direction of the rotor and the rotation center of the outer rotor is approximately 90 °, the degree of protrusion of the addendum in the rotation direction should be increased. There is an effect that the maximum compression chamber volume can be increased to obtain an almost maximum discharge amount.

Further, in the internal gear pump according to the fourth and seventh aspects, the radius of curvature of the tip circular arc is larger than 1/2 of the linear distance between the end point on the inner side in the rotor radial direction and the end point on the outer side in the rotor radial direction. Therefore, there is an effect that the gap in the vicinity of the contact point between the circular arc portion and the inner tooth is reduced to more reliably suppress the leakage of fluid from the compression chamber and further improve the volumetric efficiency.

In the internal gear pump according to the eighth and eleventh aspects, since the working fluid is sucked into the expansion chamber through the rotor suction passage formed in the outer rotor or the inner rotor, the pressure in the expansion chamber can be sufficiently maintained. Not only that, the suction efficiency can be improved by sucking the working fluid into the compression chamber through the rotor suction passage until just before the compression chamber starts compression. Further, there is a secondary effect that the weight of the outer rotor can be reduced by the amount of the formation of the rotor suction passage, and the rotational power can be reduced accordingly.

Here, in the internal gear pump according to the ninth and the twelfth aspects, since the rotor suction groove is formed on the side surface of the outer rotor or the inner rotor as the rotor suction passage, only the rotor suction groove is formed. This has the effect of reducing the shearing resistance of the hydraulic oil on the side surface of the outer rotor and reducing the rotational power.

According to a tenth aspect of the present invention, in the internal gear pump in which the rotor suction passage is formed in the outer rotor, the inner peripheral surface of the housing located radially outside the outer rotor communicates with the suction groove. Since the passage is formed and the rotor suction passage is brought to the outer peripheral surface of the outer rotor so as to connect the communication passage and the expansion chamber, it is possible to perform suction by the rotor suction passage over a wider rotation region. It is possible to further improve the inhalation efficiency.

In the internal gear pump according to a thirteenth aspect of the present invention, the suction groove is extended in the circumferential direction in the housing, and the rotor suction groove is formed so as to connect the extension portion with the expansion chamber. Therefore, there is an effect that suction can be performed by the rotor suction passage over a wider rotation region, and suction efficiency can be further enhanced. Moreover, since the extension is formed in the region radially inward of the outer teeth of the inner rotor, it does not adversely affect the ejection through the ejection groove.

In the internal gear pump described above, unlike the conventional one, it is possible to sufficiently displace the rotation centers of both rotors, and as described in claim 14, the rotation center of the inner rotor and the rotation of the outer rotor are rotated. By configuring the housing so that the amount of eccentricity with respect to the center is variable, it is possible to provide a gear pump whose pump discharge amount can be adjusted.

More specifically, in the internal gear pump according to the fifteenth aspect, there is an effect that the eccentricity amount of the rotation centers of the outer rotor and the inner rotor can be changed with a simple structure in which the cam ring is simply swung.

[Brief description of drawings]

FIG. 1 is a sectional front view showing a state in which an eccentric amount is maximum in an internal gear pump according to a first embodiment of the present invention, which is indicated by B in FIG.
It is a -B line sectional view.

FIG. 2 is a sectional front view showing a state where the eccentric amount is minimum in the internal gear pump.

FIG. 3 is a sectional view taken along line AA of FIG. 1;

FIG. 4 is a front view of a pump housing that constitutes the internal gear pump.

FIG. 5 is a front view of a cam ring that constitutes the internal gear pump.

FIG. 6 is a front view of an inner rotor that constitutes the internal gear pump.

FIG. 7 is a front view of an outer rotor that constitutes the internal gear pump.

FIG. 8 is an enlarged sectional front view showing the shapes of outer teeth and inner teeth of the inner rotor and the outer rotor.

FIG. 9 is a sectional front view showing a state in which the rotation center of the inner rotor and the rotation center of the outer rotor are aligned with each other.

FIG. 10 is a sectional front view showing an operating state of the inner rotor and the outer rotor.

FIG. 11 (a) shows that the number of external teeth and the number of internal teeth are 8
The cross-sectional front view of the inner rotor and the outer rotor set to one sheet, (b) is a cross-sectional front view of the inner rotor and the outer rotor in which the number of external teeth and the number of internal teeth are set to nine,
(C) is a cross-sectional front view of the inner rotor and the outer rotor in which the number of external teeth and the number of internal teeth are set to 10.
(D) is a cross-sectional front view of the inner rotor and the outer rotor in which the number of external teeth and the number of internal teeth are set to 11.

FIG. 12 is an enlarged sectional front view showing the shape of a rotor suction groove formed in the outer rotor.

FIG. 13A is a diagram showing a tangent line at the rotor radial inner side end point of the arc-shaped tooth tip of the external tooth and a tangent line at the rotor radial direction outer end point of the arc-shaped tooth tip of the internal tooth between each end point and the rotor rotation center. The cross-sectional front view of the inner rotor and the outer rotor whose angle formed with respect to the connecting straight line is set to 90 °, (b) is the tangent line of the arc-shaped tooth tip of the outer tooth at the rotor radial inner end point and the arc-shaped tooth tip of the inner tooth Is a cross-sectional front view of the inner rotor and the outer rotor in which the angle formed by the tangent line at the rotor radial outer end point with respect to the straight line connecting each end point and the rotor rotation center is set to 60 °. The inner rotor whose tangent line at the rotor radial inner end point and the tangent line at the rotor radial outer end point of the arcuate tooth tip of the inner tooth make an angle of 30 ° with the straight line connecting each end point and the rotor rotation center Cross-sectional front view of the fine outer rotor,
(D) is a tangent line at the rotor radial inner end of the arcuate tooth tip of the outer tooth and a tangent line at the rotor radial outer end of the inner tooth arcuate tooth tip with respect to the straight line connecting each end point and the rotor rotation center. It is a cross-sectional front view of the inner rotor and the outer rotor which set the angle formed by 0 degree.

FIG. 14 is a sectional front view of an inner rotor and an outer rotor of an internal gear pump according to a second embodiment of the present invention.

FIG. 15 is a sectional front view showing the shapes of outer teeth and inner teeth of the inner rotor and the outer rotor.

FIG. 16 is an enlarged sectional front view showing the shape of a rotor suction groove formed in the inner rotor.

FIG. 17: Conventional internal gear pump (trochoid pump)
It is a sectional front view showing an example.

[Explanation of symbols]

20 Housing Main Body 23 Pump Drive Shaft 26 Pump Housing Chamber 28 Suction Groove 28a Suction Groove 28a Suction Groove Extension 29 Discharge Portion 30 Cam Ring 36 Communication Groove 40 Inner Rotor 41 Rotor Suction Groove 42 External Teeth 42b Arc Surface (External Teeth Tip Surface) 50 Outer Rotor 51 rotor suction groove 52 inner tooth 52c arc surface (tooth tip surface of inner tooth) O ₁ center of rotation of inner rotor O ₂ center of rotation of outer rotor Oc swing center of cam ring L straight line passing through rotor center L ₄ outer tooth tip arc rotor radially inner tangential P1 external teeth tooth destination arcuate surface rotor radially outside end point P2 outer teeth tooth destination arc surface of the rotor radial direction outside end point of the tangent L ₅ Uchihaha destination arc surface in the rotor radially inner end point of the surface End point Q2 Rotor radial outer end point of internal tooth tip arc surface Q3 Rotor radial inner end point of internal tooth tip arc surface θ ₄ External tooth tip arc surface low point Formed between the straight line passing through the tangent and the end point and the rotor rotational center in the rotor radial direction outside end point of the angle theta ₅ Uchihaha destination arcuate surface straight line and forms through tangent and the end point and the rotor rotational center in the motor radially inner end point angle

Claims (15)

[Claims] 1. A housing having an inlet groove and an outlet groove on an inner side surface, and rotatably accommodated in the housing,
An outer rotor having a plurality of inner teeth arranged side by side on the inner peripheral surface, and outer teeth meshing with the outer rotor from the inner side are arranged side by side on the outer peripheral surface. An inner rotor that is rotatably accommodated is provided, and when the inner teeth and the outer teeth are in mesh with each other, the two rotors rotate synchronously to sequentially form compression chambers between the inner teeth and the outer teeth. In the internal gear pump configured to suck the fluid from the suction groove and discharge the fluid from the compression chamber to the discharge groove, the total number of external teeth and the total number of internal teeth are made equal to each other, and The shape of the outer teeth of the inner rotor is set so that the tooth tips project toward the forward side in the rotation direction of the outer rotor, while the shape of the inner teeth of the outer rotor projects such that the tooth tips project toward the backward side in the rotation direction of the outer rotor. The inner surface of the inner rotor and the inner surface of the outer rotor are fixed so that the distance in the normal direction of the inner surface of the outer rotor to the outer surface of the inner rotor is constant over the entire circumference in a state in which the rotation centers of both rotors match. An internal gear pump characterized in that the shape of the peripheral surface is set. 2. The internal gear pump according to claim 1, wherein the tips of the external teeth are set in an arc shape. 3. The internal gear pump according to claim 2, wherein an angle formed by a tangent line at the end point is approximately 90 ° with respect to a straight line connecting an end point of the circular arc portion on the inner side in the rotor radial direction and a rotation center of the inner rotor. An internal gear pump characterized in that the length of the arc portion is set so that 4. The internal gear pump according to claim 2 or 3, wherein the radius of curvature of said tooth tip arc is 1 / the linear distance between the end point on the inner side in the rotor radial direction and the end point on the outer side in the rotor radial direction of this arc portion. Internal gear pump characterized by setting larger than 2. 5. The internal gear pump according to any one of claims 1 to 4, wherein the tips of the internal teeth are set in an arc shape. 6. The internal gear pump according to claim 5, wherein an angle formed by a tangent line at the end point is approximately 90 ° with respect to a straight line connecting the outer end point of the circular arc portion in the rotor radial direction and the rotation center of the outer rotor. An internal gear pump characterized in that the length of the arc portion is set so that 7. The internal gear pump according to claim 5 or 6, wherein the radius of curvature of the tooth tip arc is 1 / the linear distance between the end point on the inner side in the rotor radial direction and the end point on the outer side in the rotor radial direction of this arc portion. Internal gear pump characterized by setting larger than 2. 8. The internal gear pump according to any one of claims 1 to 7, wherein the outer rotor extends radially outward from a peripheral surface of inner teeth of the outer rotor, and is disposed between the inner teeth and the outer teeth. An internal gear pump characterized in that a rotor suction passage is formed to connect the expansion chamber, which is formed and whose volume increases with the rotation of both rotors, and the suction groove. 9. The internal gear pump according to claim 8, wherein a rotor suction groove is formed on a side surface of the outer rotor as the rotor suction passage. 10. The internal gear pump according to claim 8 or 9, wherein a communication passage communicating with the suction groove is formed on an inner peripheral surface of the housing located radially outside of the outer rotor, while the rotor suction passage is formed. An internal gear pump having a shape in which the outer peripheral surface of the outer rotor is made to communicate with the communication passage and the expansion chamber. 11. The internal gear pump according to any one of claims 1 to 7, wherein the inner rotor extends radially inward from a peripheral surface of outer teeth of the inner rotor, and is provided between the outer teeth and the inner teeth. An internal gear pump, characterized in that a rotor suction passage is formed which connects the expansion groove, which is formed and whose volume increases with the rotation of both rotors, and the suction groove. 12. The internal gear pump according to claim 11, wherein a rotor suction groove is formed on a side surface of the inner rotor as the rotor suction passage. 13. The internal gear pump according to claim 12, wherein in the housing, the suction groove is circumferentially extended in a region radially inner than outer teeth of the inner rotor, and the extension and the expansion chamber are provided. An internal gear pump, wherein the rotor suction groove is formed so as to communicate with each other. 14. The internal gear pump according to claim 1, wherein the housing is configured so that the eccentric amount between the rotation center of the inner rotor and the rotation center of the outer rotor is variable. And internal gear pump. 15. The internal gear pump according to claim 14, wherein the housing is a housing main body, and a cam ring is provided inside the housing main body so as to be swingable about a point deviated from a rotation center of the rotors. The inner rotor is rotatably held inside the cam ring, the inner rotor is connected to a pump drive shaft, and the inner rotor and the outer rotor are driven to rotate with the rotation center of the inner ring as the cam ring swings. An internal gear pump, wherein the internal gear pump is configured to be relatively displaced.